We Keep Coding

Click event not working on dynamically added button or Panel

I am using following code in C# to add a Button
Button TextLabel = new Button(); //local variable
TextLabel.Location = new Point(0, 0);
TextLabel.Visible = true;
TextLabel.Enabled = true;
TextLabel.AutoSize = true;
TextLabel.Click += click;
this.Controls.Add(TextLabel);
And its click handler is
protected void click(object o, EventArgs e)
{
MessageBox.Show("hello");
}
Though the Button is visible and responding to mouse hover, but nothing is happening on its click. What could be wrong or missing?
If I write this same code in an independent project, it works!!!!! Strange. but why????
Form Properties: (if required)
1. Show in taskbar: false
2. Borderless
3. 50% Opaque

Today I realised that just registering click event for a control will not make any event to work unless its parent (in my case its form) on which that control is still active.
Parent control will receive event notification earlier than its child controls. This is a simple and obvious observation, but if not paid attention will make undesirable effects.
That's the mistake I did, I made another form active on my form activated event, hence any control in it didn't received events like mouse clicks.
Talking of 'hover effects are working', then yes, even if a form is inactive, hover works.
So I just removed the line of code that made another form active and everything is working fine now.
private void Form1_Activated(object sender, EventArgs e)
{
//if (form2!=null) form2.BringToFront(); //commented this
}

Stop TextChanged event from firing Leave event

I'm working on a simple WinForms application for a public school where users can identify themselves by entering either their network IDs (which are not protected information) or their system IDs (which are protected information). I want to switch to a password character when the program detects a system ID (which is working just fine); however, when I do this, my application also fires the textbox's Leave event, which tells users to fix a problem with the login data...before there's even a problem.
Here's my code:
void login_TextChanged(object sender, EventArgs e)
{
login.UseSystemPasswordChar = login.Text.StartsWith(<prefix-goes-here>);
}
private void login_Leave(object sender, EventArgs e)
{
if (login.Text.StartsWith(<prefix-goes-here>) && login.Text.Length != 9)
{
signInError.SetError(login, "Your System ID must be nine digits.");
login.BackColor = Color.LightPink;
}
else if (login.Text.IsNullOrWhiteSpace())
{
signInError.SetError(login, "Please enter your username or System ID.");
login.BackColor = Color.LightPink;
}
else
{
signInError.SetError(login, string.Empty);
login.BackColor = Color.White;
}
}
Ultimately, I don't know that this will cause a ton of problems, and I could move this validation step to the Click event of the sign in button on my form, but I'd rather do validation piece-by-piece if possible.

Putting the TextBox inside a GroupBox does reproduce that behavior-- which is odd.
If you want to keep your GroupBox, here is a work around:
private void login_TextChanged(object sender, EventArgs e)
{
login.Leave -= login_Leave;
login.UseSystemPasswordChar = login.Text.StartsWith(<prefix-goes-here>);
login.Leave += login_Leave;
}

For whatever reason, the Leave event fires when the login TextBox is inside a GroupBox control. Replacing the GroupBox with a simple Label control prevented the code within the TextChanged event from firing the Leave event.

Yes, this is a quirk of the UseSystemPasswordChar property. It is a property that must be specified when the native edit control is created (ES_PASSWORD). Changing it requires Winforms to destroy that native control and recreate it. That has side-effects, one of them is that the focus can't stay on the textbox since the window disappears. Windows fires the WM_KILLFOCUS notificaiton.
Being inside a GroupBox is indeed a necessary ingredient, Winforms doesn't suppress the Leave event when it gets the notification. Bug.
Many possible fixes. You could set a flag that the Leave event handler can check to know that it was caused by changing the property.

How to capture mouse wheel on panel?

How to capture mouse wheel on panel in C#?
I'm using WinForms
EDIT:
I try to do it on PictureBox now.
My code:
this.pictureBox1.MouseClick += new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseClick);
this.pictureBox1.MouseWheel += new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseClick);
private void pictureBox1_MouseClick(object sender, MouseEventArgs e)
{
MessageBox.Show("Click");
}
Clicking works. Wheelling doesn't.
Why?

If you can't see the "MouseWheel" event on a component, then you need to create it manually. Also, we need to focus that component, otherwise the "MouseWheel" event will not work for that component. I will show you how to create a "MouseWheel" event for "pictureBox1" and how it works.
INSIDE THE CONSTRUCTOR, create a mousewheel event on that component.
InitializeComponent();
this.pictureBox1.MouseWheel += pictureBox1_MouseWheel;
CREATE THE FUNCTION manually. According to my example, call it "pictureBox1_MouseWheel"
private void pictureBox1_MouseWheel(object sender, MouseEventArgs e)
{
//you can do anything here
}
CREATE a MouseHover event on that component (Go to properties in PicureBox1, select event, locate "MouseHover" and double-click the "MouseHover" event).
CALL "Focus()"; method inside that MouseHover event.
pictureBox1.Focus();
Now run the program.

Windows sends the WM_MOUSEWHEEL message to the control that has the focus. That won't be Panel, it is not a control that can get the focus. As soon as you put a control on the panel, say a button, then the button gets the focus and the message.
The button however has no use for the message, it's got nothing to scroll. Windows notices this and sends the message to the parent. That's the panel, now it will scroll.
You'll find code for a custom panel that can get the focus in this answer.
UPDATE: note that this behavior has changed in Windows 10. The new "Scroll inactive windows when I hover over them" option is turned on by default. The makes the mouse wheel behavior more consistent with the way it works in a browser or, say, an Office program. In this specific case the picturebox now will get the event. Watch out for this.

To wire it up manually...
this.panel1.MouseWheel += new System.Windows.Forms.MouseEventHandler(this.panel1_MouseWheel);
private void panel1_MouseWheel(object sender, System.Windows.Forms.MouseEventArgs e)
{
///process mouse event
}
Easier method is in visual studio click on panel, goto properties viewpanel, select events, locate and double click the "mousewheel" event.

In Winforms, this is achieved using the Control.MouseWheel event

Getting mousewheel events is tricky. The easiest way is using
this.MouseWheel += new System.Windows.Forms.MouseEventHandler(this.panel1_MouseWheel);
instead of
this.panel1.MouseWheel += new System.Windows.Forms.MouseEventHandler(this.panel1_MouseWheel);
This way the form gets the event instead of control. This way is easy but has one problem: you can use only one mousewheel event in your form.
If you have more than one control to get mousewheel event the best way is This answer by "Shehan Silva - weltZ"

C# TreeView SetFocus firing leave event twice

I have this simple code, where when the user leaves the TextBox control, TreeView gets focused:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
this.treeView1.Nodes.Add("A");
this.treeView1.Nodes[0].Nodes.Add("A.A");
this.treeView1.Nodes.Add("B");
this.treeView1.Nodes[0].Nodes.Add("B.A");
}
private void textBox1_Leave(object sender, EventArgs e)
{
System.Diagnostics.Debug.WriteLine("Leave..");
this.treeView1.Focus();
}
}
If we execute this code the Leave event is fired twice:
Leave..
Leave..
But if we set focus to other control, only one Leave event is fired.
Is that a problem of the TreeView? Do you know any workaround? Should we report this to Microsoft?
Thanks,
RG

this.treeView1.Focus();
Do not use the Focus() method in an event handler that's called because of a focusing event, like Leave. If you need to prevent a focus change then use the Validating event instead. Setting e.Cancel = true stops it.
But do note that this isn't very logical to do so for a TreeView, there isn't anything the user can do to alter the state of the control. You'll trap the user. Maybe that was the intention, do make sure the user can still close the window. If not then you might need the FormClosing event to force e.Cancel back to false.

Given that there is no code there to wire up the event I'm guessing you did it from the designer which means a line of code such as
textBox1.Leave += new EventHandler(textBox1_Leave);
will have been added to the Form1.designer.cs, check this file to ensure the line doesn't exist more than once as for each time this line is run you will get an event trigger, so if you run the line 3 times the Leave event will fire 3 times when you leave the textbox!
HTH
OneShot

How to stop textbox leave event firing on form close

using c# winforms vs2008
I've got a textbox on a form with a method being called from the textBox1_Leave event. The method takes the contents of the textbox in question and populates other textboxes based on the contents.
My problem is that is the user has focus on the text box then clicks the button to close the form (calling this.close) then the form does not close because the textbox leave event gets fired.
If the textbox does not have focus on form close then the form closes fine.
If however a user closes the form by clicking the little X close icon in the top corner the it closes fine all the time with out the textbox leave event being fired.
How can I duplicate the X close functionality so that I can always close the form without the textbox leave event being fired?

The simplest solution is going to be to check which control is actually focused before doing your post-processing - but you can't do it in the Leave handler, because the focus will still be on the text box at that point.
Instead, you need to move your logic to the LostFocus event, which is not in the designer. You'll have to wire it up at runtime:
public class Form1 : Form
{
public Form1()
{
InitializeComponent();
textBox1.LostFocus += new EventHandler(textBox1_LostFocus);
}
private void textBox1_LostFocus(object sender, EventArgs e)
{
if (closeButton.Focused)
return;
// Update the other text boxes here
}
}
The LostFocus event happens to fire after the new control receives focus.
Clarification - you might find that it works by putting this logic in the Leave event - if the focus is changed by the mouse. If the keyboard is used instead, you'll get the wrong behaviour. LostFocus is reliable in both cases - the focused control will always be the "new" control. This is documented on MSDN: Order of Events in Windows Forms.
Incidentally, the reason why you're not having this problem with the "red X" is that the X is not actually a control that can receive focus, it's part of the window. When the user clicks that, it's not causing the text box to lose focus, and therefore isn't causing the Leave event to fire.

Another approach:
Use the textbox's validating event instead of it's leave event, then change the button's CausesValidation property to false. You will also have to set the textbox to not cause validation in the button's click event so the validating event will not fire when the form is closing (thanks to #Powerlord for pointing this out).
private void button1_Click(object sender, EventArgs e)
{
this.textBox1.CausesValidation = false;
this.Close();
}

You could also handle the FormClosing event and make sure the e.Cancel argument does not get set to true by the validating events on the other controls on the form. I think they will be fired off before the FormClosing event.
private void MainForm_FormClosing(object sender, FormClosingEventArgs e)
{
if (e.CloseReason == CloseReason.UserClosing)
{
e.Cancel = false;
return;
}
}

you can check to see which control has just got focus.
private void textBox1_Leave(object sender, EventArgs e)
{
if (btnClose.Focused)
return;
// go from here
}

Just check if the form owning the textbox is disposing? If it's getting closed, it's disposing. If it's disposing you could simply end the pesky 'leave' event without doing anything. I didn't check it and forgive me, I'm choked on a project of my own so and I was searching myself, so I don't think I'll have time for that.
private void GuiltyTextBox_Leave(object sender, EventArgs e) {
Form formOwningTheTextBox=(Form)((Control)sender).TopLevelControl;
if (formOwningTheTextBox.Disposing || formOwningTheTextBox.IsDisposed) return;
.......
}
I just believe this is going to work with minimum effort and wanted to send a quick answer before I resume searching my own answer.

Write Following line of code in text box leave event on top
if me.closing then
return
end if